The Pro-Ject 87g Counterweight (043) is a genuine replacement counterweight for Pro-Ject tonearms in the Evolution range. 043 is Pro-Ject's part code for the counterweight itself, not a tonearm designation: Henley Audio, Pro-Ject's UK distributor, lists the part as 1940875043 with a block weight of 87g, and Pro-Ject's own counterweights database records the same component as CC/AS 08 (43) at 87g.
Counterweight choice is governed by cartridge mass. On the 9CC Evolution tonearm (sold today as the EVO CC 9") the 043 covers cartridges weighing 9.0g to 11.0g. On the X1 and X1 B tonearm, which also uses Evolution counterweights, it covers 9.0g to 12.0g. If your cartridge falls outside those figures, another weight in the series will balance the arm more accurately.
The counterweight is a damped aluminium design with an inner tracking force scale ring, using TPE damping to counteract unwanted resonances. Pro-Ject supplies two counterweights with each EVO CC tonearm so that the one sitting closest to the bearing block can be chosen for the tracking force in use, which keeps the arm stable and its inertia low.
Turntables listed by Henley Audio as taking the 043: Pro-Ject RPM 5 Carbon, RPM 9 Carbon, RPM 9.2 Evolution, X1, X1 B, 2Xperience, 2Xperience (DC), 2Xperience SB Sgt. Pepper Limited Edition, 2Xperience Vivo Blue, 2Xperience Rondo Red, The Beatles White Album, Xtension 9, Xtension 9 SuperPack, 6PerspeX, 6PerspeX SB, 6PerspeX Balanced and 6PerspeX Balanced UK SuperPack.